This disclosure relates to polycarbonate compositions and articles formed from such compositions that exhibit a matte, or non gloss or luster, surface appearance and high light transmission, as well as uses thereof.
Polycarbonates (PC) have excellent mechanical properties including impact resistance, thermal stability such as heat resistance, and optical properties such as transparency, among others. These materials are therefore widely used in various applications such as in mechanical or structural parts, and automobile components, as well as optical applications, such as lenses, optical memory disks, and optical fibers, etc.
However, articles made with polycarbonates generally exhibit high gloss or luster, which is not desirable for applications such as anti-glare lenses, ATM screens, decorative articles, and housings for electronic appliances such as computers. As a result, transparent polycarbonate resins that can readily be formed with matte, low gloss and/or shine surface appearances are needed.
Since matting agents, such as inorganic fillers and rubbers, cause polycarbonates to be opaque, the most widely used technologies to produce a matte surface include textured molds and matte coatings. However, textured molding methods need special mold modifications, and, after articles are released from such a mold, the relatively hot surfaces tend to relax and reduce the surface roughness of the resulting article, thereby increasing its gloss. Furthermore, matte coating is not only less cost-effective, but also undesirable for the purposes of environment protection.
EP0730624 discloses a low gloss transparent PC. In that document, a high molecular weight branched PC (Mw above 99,100) is mixed with linear PC. The blends exhibit a good combination of physical properties, thermal stability, color, melt strength, transparency and matte surface. However, the high viscosity of branched PC poses a problem for molding operations.
In EP054497, a polycarbonate with a reactive end group sealer is blended with a radical initiator and normal linear PC. Lower gloss and relatively high light transmission (around 84%) are achieved through this reactive extrusion process. However, reactive extrusion processes result generally in poor consistency, and reduced production output. Moreover, the light transmission of the product is usually not very satisfactory.
There accordingly remains a need in the art for polycarbonate compositions that can readily produce an article with a matte surface and high light transmission, which is also thermally stable, cost-effective, and have good manufacturability characteristics, among others.